1. Field of the Invention
The present invention relates generally to medical devices and, more particularly, to syringes and needles.
2. Description of Related Art
The term “stress urinary incontinence” refers to a functionally insufficient urinary tract of a patient. In a patient having this condition, the tissue relaxation of the sphincter mechanism, located at the urinary outflow of the bladder into the urethra, can cause a loss of bladder control. Cystoscopes are typically used to study the urethra and bladder and to evaluate a patient's urinary incontinence condition. A typical cystoscope may comprise a tubular instrument equipped with, for example, a visual channel and a working channel, and constructed to be inserted through the urethra for viewing of the urethra and bladder. Treatment of a urinary incontinence condition may comprise the injection of a filler material, such as collagen, into and adjacent to the urinary sphincter muscle at the bladder neck, to thereby bulk up the tissue and assist in the adequate closure of the urinary sphincter.
Acid reflux is a digestive disorder which similarly involves the tissue relaxation of a sphincter mechanism. In the case of acid reflux, which is commonly known as gastroesophageal reflux disease (GERD) or heartburn, the lower esophageal sphincter connecting the esophagus to the stomach begins to malfunction. During proper operation of the lower esophageal sphincter, the lower esophageal sphincter opens to allow food to pass into the stomach and closes to prevent food and acidic stomach fluids from flowing back up into the esophagus. Gastroesophageal reflux occurs when the lower esophageal sphincter is weak or relaxes inappropriately, allowing the stomach's contents to retrograde or flow up into the esophagus. This retrograde flow of gastric contents back into the esophagus, through what should be a one-way valve into the stomach, can damage the esophagus. More particularly, the contents of the stomach are very acidic; and the lining of the stomach is specially designed to cope with the lower pH contents. The esophagus, on the other hand, is not suited for such exposure to highly acidic materials. Thus, when acid retrogrades from the stomach into the esophageal tissues, irritation and inflammation will often result to these tissues.
The severity of tissue damage which can result from gastroesophageal reflux disease can depend on factors such as the dysfunctional level of the lower esophageal sphincter, the type and amount of fluid brought up from the stomach, and the neutralizing effect of the patient's saliva. Another factor, which may affect the severity of a particular gastroesophageal reflux disorder, is the patient's esophageal motility. Lack of esophageal motility can occur through either of two mechanisms. When incomplete emptying of the esophagus into the stomach after ingestion of liquids or solids occurs, the motility of the esophagus can be said to be effected, resulting in esophageal reflux. Also, esophageal reflux can occur when small amounts of gastric contents, which may be refluxed into the lower esophagus, are not rapidly emptied back into the stomach. Delays in the emptying of this material, caused by an esophageal motility disorder, for example, can lead to irritation of the esophageal mucosa and possibly to the sensation of heartburn or the development of esophagitis.
Various tools and instruments have been used in the prior art for the treatment of urinary incontinence and acid reflux disease. Gastroscopes are typically used to study the esophagus and to evaluate, for example, a patient's acid reflux condition. A gastroscope typically comprises a flexible, lighted instrument that is inserted through the mouth and esophagus to view the stomach. Similarly, a cystoscope is typically inserted through a patient's urethra to facilitate evaluation of, for example, a urinary incontinence condition.
A viscous material, such as collagen, may be injected into the vicinity of either the lower esophageal sphincter (for acid reflux) or the sphincter of the urethra (for urinary incontinence) to treat either of the above-mentioned disorders. These injection procedures typically involve elongated catheters for the delivery of viscous materials through the body passages and to the target sites of injection. The force required to deliver a viscous material through the delivery lumen of an elongated catheter will increase as the average viscosity of the material being delivered is increased and will also increase as the length of the elongated catheter increases.
To compensate for the greater required force, it would be desirable to form the elongated catheter to have a lumen with a relatively large cross-sectional area to facilitate flow of the viscous material therethrough. Another design criterion is that the diameter of the needle tip should be relatively small to reduce tissue trauma at the injection site, to increase precision in some instances, and to reduce patient discomfort.
In order to meet the objectives of both a relatively large delivery lumen and a relatively small needle tip, a juncture must be formed at some point along the length of the needle to transition the needle diameter from a relatively large size to a relatively small size. If the transition point is abrupt or too great in magnitude, optimal flow of the viscous material through the needle may be inhibited.